Modern motor vehicles have, for example, what are known as pixel headlights, with which it is possible to drive individual light points, or pixels, in larger matrix. By individually driving each pixel in this manner, it is possible to selectively illuminate individual regions in front of the motor vehicle using a corresponding motor vehicle headlight.
A pixel headlight is realized, for example, by a matrix of LEDs. This gives a light-emitting surface, which can also be referred to as an LED surface, a chip surface or an LED having high pixilation.
The largest possible size of a monolithically produced light-emitting surface in the case of semiconductor light sources is limited due to production technology. If the aim is to generate a larger light-emitting surface, it is necessary for the light source having this size or above to be divided into a plurality of individual LED surfaces and to arrange them as closely together as possible so as to achieve a luminance that is as homogeneous as possible over the entire surface. The illumination apparatus which is attainable hereby thus has a matrix-type structure.
For reasons of production technology, however, it is necessary to maintain a gap between the individual light-emitting devices, i.e. the LED surfaces or chip surfaces. This gap is produced due to the fact that it is necessary, for example, for a single chip, produced by epitaxy, having high pixilation to be scribed at the edge using diamonds and subsequently broken, or alternatively to be sawn. In such a separation method, a tolerance region must be observed at the edge so as to not damage the external LEDs. If two such chips or light-emitting devices are joined together, a corresponding gap for example of 0.02 to 0.12 mm is formed between them. Due to this gap, a drop in luminance occurs in the luminance distribution over the entire surface.
The LEDs or the chip surfaces can be directly emitting light-emitting diodes, i.e. light-emitting diodes that emit substantially in monochrome in the visible, infrared or ultraviolet spectral range, and/or what are known as phosphor-converting light-emitting diodes (in this case preferred), i.e. light-emitting diodes in which e.g. blue light emission from the semiconductor chips is incident on a phosphor that is applied on the chip surface. The phosphor, also referred to as conversion element, can for example here be a yellow cerium-YAG-phosphor (Ce:YAG) that partially converts the blue excitation radiation into yellow conversion light. The superposition of non-converted blue excitation light and yellow conversion light then produces the used light that has a blue-white, white or yellow-white color impression, depending on the degree of conversion of the phosphor arrangement. In the automotive industry, the color point of a light source of a front headlight for low beam and high beam is regulated by the ECE standard.
It is therefore the object of the present disclosure to provide a method with which it is possible to better avoid a marked reduction in the luminance distribution in a gap between two light-emitting devices when driving an illumination apparatus. Moreover, a corresponding illumination apparatus is to be proposed.